The present invention relates to a curable, anti-microbial silicone rubber composition.
Silicone rubber compositions have been widely used in industry for a wide variety of different applications. These applications include for example pan grips, camera eye caps, handles of bicycles, slipping preventors for spectacles, various rubber sheets and rubber coated cloth such as sheets and curtains that are used for example in hospitals. Silicone rubber compositions are further used as tubes and backings for food containers or various kinds of hygienic appliances. In many of these applications, there is a demand for anti-microbial and anti-fungal efficacy of the silicone rubber compositions. This demand stands from the fact that many of the usage environments are prone to microbial or fungal contamination. For example, such usage environments include the presence of contaminated surfaces such as to and/or the presence of ambient wetness in combination with room or even higher temperatures.
In Japanese patent application 7-65149, filed on Feb. 28, 1995, it has been suggested to incorporate into a silicone rubber composition and inorganic anti-microbial agent, the agent comprising silver loaded on an inorganic material such as a zeolite, a zirconium phosphate, or a calcium phosphate. Such silicone 30 rubber compositions, however, are only capable of releasing the silver atoms in ionic form and hence are cytotoxic.
It is therefore an object of the present invention to provide a silicone rubber composition, which overcomes the disadvantages of the prior art silicone rubber compositions.
It is a further object of the present invention to provide a silicone rubber composition, which is anti-microbial by releasing silver atoms.
It is a further object of the present invention to provide a silicone rubber composition, which is anti-microbially effective whilst not being cytotoxic.
The present invention provides an anti-microbial, curable silicone rubber composition comprising in at least a portion of the exposed surface of said composition an organic matrix containing homogeneously dispersed particles of metallic silver having a particle size in the range of 1 to 50 nm (silver nanoparticles) in an amount providing on the surface of said composition an anti-microbially effective but less than cytotoxic silver concentration.
The present invention further provides a silicone rubber composition, characterized by comprising said silver nanoparticles in an amount providing a silver concentration of from more than 1 nmol/1 to less than 1 xcexcmol/1 on at least a portion of the surface of said composition.
The present invention further provides a silicone rubber composition, characterized in that said organic matrix comprises said silver nanoparticles in an amount of 1 to 2000 ppm, preferably 5 to 1000 ppm and more preferably 10 to 250 ppm.
The present invention further provides a silicone rubber composition characterized by comprising silver nanoparticles having a particle size of 2 to 20 nm preferably 5 to 10 nm.
The present invention further provides a silicone rubber composition characterized in that said fluid organic matrix comprises an organic fluid wherein said silver nanoparticles are dispersed.
The present invention further provides a silicone rubber composition characterized in that said viscous organic fluid comprises an aliphatic or aromatic hydrocarbon, a mineral oil, petrolatum, glycerol, a fatty alcohol, polypropylene lo glycol, an animal and/or vegetable oil or fat, or a silicone oil.
The present invention further provides a method for manufacturing a curable, anti-microbial silicone rubber composition comprising the steps of:
providing a curable silicone rubber composition in a configuration ready for mixing
providing a liquid organic matrix comprising metallic silver having a particle size in the range of 1 to 50 nm
mixing said liquid organic matrix into said silicone rubber compositionxe2x80x94optionally curing the mixture of said composition with said organic matrix